Electrically-powered trolling motors are used to slowly propel a boat used in fishing through the water, to provide relative movement between the water and the bait being used, to provide a more lifelike appearance to the bait. A storage battery is used as the source of direct current power, and conventionally a tapped dropping resistor is connected between the source of direct current power and a direct current motor, coupled to a propeller. This tapped dropping resistor may be in a separate enclosure within the boat, or, in one commercially-available system, includes a tapped resistor formed by wire wound in a manner to conform to the inner surface of a housing containing the direct current motor. The housing is submerged in use, and the proximity of the wire forming the tapped resistor to the housing provides cooling for the resistor. Providing separate dropping resistors in a separate housing is both expensive and bulky, and the technique of winding wires about the inner surface of a submersible housing is difficult and costly to manufacture. The instant invention overcomes these and other deficiencies of the known prior art.